Goals: Pioneer P-3 was intended to orbit the Moon, take photographs and study the interplanetary environment with a variety of sensors. It was the first mission to use an two-stage Atlas rocket that allowed heavier payloads to be hurled into space.

Accomplishments: None. Forty-five seconds after liftoff, the spacecraft's nose fairing broke away and the rocket tumbled and exploded. Contact was lost 104 seconds after launch.